Devices for supplying respiratory gas are used particularly in the treatment of respiratory ailments of adult or infant patients.
Such devices are adapted to supply a quantity of air, if desired with added oxygen, either in the form of a quantified breathable volume, or in the form of a first predetermined pressure called inspiration pressure and a second predetermined pressure called expiration pressure.
WO 00/24447 relates to a device for supplying respiratory gas provided with a compressor delivering a flow of gas under pressure to a patient through a downstream accumulator/silencer and a flow rate regulating valve. According to this document, the surplus of unneeded gas is returned to an upstream filter/accumulator through a bypass valve so as to limit the loss of respiratory gas.
FR 2 663 547 A1 relates to apparatus for continuously providing an overpressure of respiratory gas; this apparatus using a high speed turbine supplying gas under constant predetermined pressure regulated by measuring the pressure at the respiratory mask of the patient. This apparatus is passive in that the pressure is maintained continuously, the expiration phases being possible thanks to a calibrated loss at the respiratory mask of the patient.
FR 2 822 384 A1 in the name of the applicant relates to a mixed pulmonary ventilator provided with a flow generator, the circulation means permitting re-injecting the flow upstream of the generator during an expiration phase of the patient, the circulation means comprising particularly a regulating valve comprising two flaps actuated by the same actuator permitting several modes of regulation and an optimization of the flow as a function of the inspiration and expiration phases. According to this document, the speed of rotation of the generator is maintained constant, the pressure in the patient circuit being controlled by the two flaps which permit return of the gas to the generator particularly during the expiration phases.